The invention relates to varying the loop engageability of arrays of molded fastener elements, and to the formation of fastener products with exposed grip flanges.
Hook components for hook and loop fastening include a base from which tiny fastener elements (e.g., hook-shaped or mushroom-shaped elements) extend in an array. Hook components with hook-shaped elements may be formed by integrally molding the base and fastener elements in a continuous process employing a mold roll that includes a set of stacked disk-shaped mold plates having fastener-shaped cavities defined at their peripheries, e.g., as described in U.S. Pat. No. 4,794,028 (Fischer), the full disclosure of which is incorporated herein by reference. Hook components may also be injection molded as discrete parts. In the Fischer process, it is generally preferable that the entire molding region of the mold roll include an even distribution of mold cavities, to promote uniform resin flow and molding pressures over the mold roll surface and also to avoid uneven demolding stresses that could distort the fastener. To produce fastener products of the same resin but with different loop engagement characteristics, manufacturers either vary the hook density by changing the spacing between adjacent rows of hooks, or replace the mold plates with others having a different hook cavity shape or in-row spacing.
To form a closure, male fastener elements engage overlying female fastener elements. When the male element is hook-shaped, the fastener element will individually exhibit directional shear strength, i.e., the shear strength in one direction will be significantly higher than in other directions. In some applications it is desirable that the array of fastener elements exhibit bidirectional shear strength, i.e., shear strength substantially equal in each of two opposite directions. To accomplish this, some fastener products include arrays of hooks in which a plurality of rows of fastener elements are arranged so that, in each row, all of the crooks face in the same direction and parallel to the direction of the row, and so that the crooks of adjacent rows face in opposite directions, as shown in FIG. 1.
It is often desirable for a hook and loop fastener to have areas in which there is no engagement or a reduced strength engagement of the two sides of the fastener. Such areas may, for example, be associated with a gripping tab to enable the user to more easily separate the two parts of the fastener.
The present invention features, in several aspects, an array of hook-shaped fastener elements in which the relative spacing between adjacent hooks varies across the array such that some of the fastener elements are rendered less capable of engagement with loop elements than other fastener elements.
In preferred fastener products, the hook elements are arranged so that some of the hook elements interfere with adjacent hook elements to prevent engagement of the hook elements with loop elements. Advantageously, for fastener products that are molded on mold rolls that include a stack of registered mold plates, e.g., as described in U.S. Pat. No. 4,794,028 (a xe2x80x9cFischer processxe2x80x9d), this arrangement can be accomplished by simply adjusting the registration of the mold plates, without the need for other process or tooling changes.
In one aspect, the invention features an array of hook-shaped fastener elements arranged in parallel rows, each fastener element including a stem and a crook extending from the stem in a predetermined direction to a distal tip. The array includes a plurality of rows of fastener elements arranged such that, in each row, all of the crooks face in the same direction and parallel to the direction of the row, and such that the crooks of adjacent rows face in opposite directions. The longitudinal spacing between opposing tips of adjacent hooks of adjacent rows is greater, in a first portion of the array, than the longitudinal spacing between opposing tips of adjacent hooks of adjacent rows in a second portion of the array. As a result, the crooks of the hooks of the first portion of the array are more exposed for engaging loops than the crooks of the hooks of the second portion of the array.
In preferred implementations, the crooks of the hooks of adjacent rows in the second portion of the array overlap each other in side profile to interfere with the ability of the crooks to engage loop elements.
In another aspect, the invention features a fastener product that includes (a) a first fastener component comprising a common base and an array of hook-shaped fastener elements arranged in parallel rows on the common base, and (b) a second fastener element, comprising a common base and a plurality of loops extending from the base for engagement with the hooks. Each fastener element includes a stem and a crook extending from the stem in a predetermined direction to a distal tip, and the array includes a plurality of rows of fastener elements, arranged so that, in each row, all of the crooks face in the same direction and parallel to the direction of the row, the crooks of adjacent rows face in opposite directions. The longitudinal spacing between opposing tips of adjacent hooks of adjacent rows is greater, in a first portion of the array, than the longitudinal spacing between opposing tips of adjacent hooks of adjacent rows in a second portion of the array. As a result, the crooks of the hooks of the first portion of the array are more exposed for engaging loops than the crooks of the hooks of the second portion of the array.
In preferred implementations, the product includes a strip of fastener tabs or a fastener tape.
In some cases, the product includes a personal care product. By xe2x80x9cpersonal care productxe2x80x9d as used within this patent application, we mean diapers, training pants, swim wear, absorbent underpants, adult incontinence products and feminine hygiene products.
In another aspect, an absorbent article is provided. The article has a flexible sheet for fitting about the body of a wearer, the flexible sheet having a first waist portion and a second waist portion. A first fastener element is coupled to the first waist portion, having a common base and a plurality of loops extending from the base. A second fastener component is coupled to the second waist portion such that the second fastener component can be brought into contact with the first fastener element when the first waist portion and the second waist portion are fitted about the body of a wearer. The second fastener component has a common base and an array of hook-shaped fastener elements arranged in parallel rows on the common base, with the fastener elements arranged as described above so as to enhance the grippability of the second fastener component.
In another aspect, the invention features a method of forming an array of fastener elements extending from a common base. The method includes providing a mold having a mold surface from which an array of fixed mold cavities extend inwardly. Each mold cavity defines a hook including a stem and a crook extending from the stem in a predetermined direction, with the array including a plurality of rows of cavities arranged such that, in each row, all of the crooks face in the same direction and parallel to the direction of the row, and with the crooks of adjacent rows face in opposite directions. The registration of adjacent rows is adjusted so that the longitudinal spacing between opposing tips of adjacent hooks of adjacent rows in a first portion of the array is greater than the longitudinal spacing between opposing tips of adjacent hooks of adjacent rows in a second portion of the array, such that the crooks of the hooks of the first portion are more exposed for engaging loops than the crooks of the hooks of the second portion. Moldable resin is delivered to the mold, thereby filling the mold cavities and forming the common base. The resin is solidified in the cavities to form the fastener elements, which are then removed from their corresponding fixed mold cavities by pulling the common base away from the mold surface.
In some implementations the method further includes forming the mold cavities by aligning a plurality of mold plates in face to face relation, registered openings in the aligned mold plates defining the mold cavities.
The adjusting step may include rotating at least some of the mold plates relative to other mold plates.
In some cases the mold plates are disk-shaped and, when aligned, form a mold roll, the mold cavities extending inwardly from a peripheral surface of the mold roll.
The delivering step includes, in some embodiments, extruding molten resin into a nip defined between the mold roll and a pressure roll.
In another aspect of the invention, a method is provided for varying the loop engagement characteristics of a molded fastener product produced with a set of mold plates arranged in face-to-face relation to form an array of fastener element mold cavities, with each mold plate defining one of many rows of cavities of the array. The method includes positioning the mold plates to purposefully set the longitudinal registration of adjacent rows of the array to decrease longitudinal spacing between adjacent fastener element cavities of adjacent rows, to produce a fastener product with at least a region of an array of fastener elements having a lower loop engageability than a fastener product molded with the mold plates in a different position.
The invention also features, in another aspect, a mold for forming a fastener device. The mold has a mold body with a surface on which a common base can be molded, and defines an array of mold cavities extending into the mold body from the surface. The mold cavities are arranged in parallel rows, with each fastener element including a stem and a crook extending from the stem in a predetermined direction to a distal tip. The array includes a plurality of rows of fastener elements arranged such that, in each row, all of the crooks face in the same direction and parallel to the direction of the row, with the crooks of adjacent rows facing in opposite directions. The longitudinal spacing between opposing tips of adjacent hooks of adjacent rows in a first portion of the array is greater than the longitudinal spacing between opposing tips of adjacent hooks of adjacent rows in a second portion of the array, such that the crooks of the hooks of the first portion are more exposed for engaging loops than the crooks of the hooks of the second portion.
The invention also features a strip of continuously molded fastener tape and a die cut strip of fastener tabs, having the features described above.
In yet another aspect, the invention features an array of hook-shaped fastener elements arranged in parallel rows, each fastener element including a stem and a crook extending from the stem in a predetermined direction to a distal tip, the array having a substantially constant hook density over its surface, and a first portion of the array being constructed to engage loops to a greater extent than a second portion of the array.
In a further aspect, the invention features an array of male fastener elements arranged in parallel rows, each fastener element including a stem and a loop-engaging portion extending from the stem, the array including a plurality of rows of fastener elements. The longitudinal spacing between loop-engaging portions of opposing pairs of fastener elements of adjacent rows in a first portion of the array is greater than the longitudinal spacing between loop-engaging portions of opposing pairs of fastener elements of adjacent rows in a second portion of the array, such that the loop-engaging portions of the fastener elements of the first portion are more exposed for engaging loops than the loop-engaging portions of the fastener elements of the second portion.
In some implementations the male fastener elements are mushroom shaped.
The invention also features an array of male fastener elements arranged in parallel rows, each fastener element including a stem and a loop-engaging portion extending from the stem, the array having a substantially constant hook density over its surface, and a first portion of the array being constructed to engage loops to a greater extent than a second portion of the array.
The invention can provide, inter alia, the advantage of increasing the grippability of engaged fastener tabs without increasing their manufacturing costs. This can be particularly valuable on diapers and other garments, and on fasteners securing emergency medical or fire-fighting equipment. In another sense, the invention can provide the advantage of providing a grip tab with a reduced, but not negligible, amount of loop engageability, such that the grip tab can itself be lightly secured to a loop surface. As applied to diaper tabs, this can make the tab less susceptible to being manipulated by an infant or becoming undesirably released during infant movement. In conjunction with the multiple-plate molding method, where each plate forms one of several rows of fastener elements, the invention is readily implemented by shifting the longitudinal registration of adjacent plates to skew the spacing of adjacent fastener elements to either enhance or degrade their loop engageability. Such registration manipulation is also useful for enabling the molding of fastener products with differing loop engagement characteristics with a single set of mold plates. Such plates can be very expensive to manufacture, and a shift in registration can be much less expensive than having multiple sets of plates of different hook cavity shapes or in-row spacings.
Other features and advantages of the invention will be apparent from the following description of a presently preferred embodiment, and from the claims.